A plant of this type is known from EP2340982, comprising an assembly line divided into two sections, which are mounted one above the other, the first beneath the second. A plurality of pallets, on which the mechanical parts to be assembled on each body are arranged in sequence and according to a pre-established layout, are moved along the first section in a first determined direction. The completed pallets are then moved to the second section by an elevator, and here they are moved in a second direction, opposite to the first, after having had a body coupled to each pallet, the body being brought to the plant by a conveyor that is not part of the plant. Each of the bodies is thus supported by a corresponding pallet, directly on the pallet together with the parts to be assembled. Once assembly of the mechanical parts carried by each pallet on the respective body is completed, the latter and the pallet are separated and the pallet is returned, empty, to the first section by means of a lowerator, for being used again.
The plant described, although satisfactory, has several drawbacks. To start with, it requires a series of operations to separate the bodies from the conveyor and then mount them on it again or on another conveyor, and to mount and dismount the bodies on/from the pallets, operations that can also require the involvement of one or more workers. Furthermore, the body can be subjected to undesired mechanical stress during assembly operations.